Wastewater Recycling

Normally local potable water is supplied via tanker truck or fire hydrant for Hydrodemolition. Consumption rates can range from 8,000 to 30,000 gallons a day depending on the number of pump hours and type of pumps being used. To reduce consumption and discharge, it is possible to recycle the wastewater generated from the operation. Water can be collected and put into and processed by a special treatment system for reuse. Because the high-pressure water pumps and nozzles are extremely susceptible to wear from abrasive materials in the water, the recycled water must be carefully filtered to remove suspended and dissolved solids. This can be done through use of large settling areas, flocculants and specialty filtration equipment.

Assuming that the treatment goal is a fixed target, then any water treatment depends on three variables; time, space and money. If you have a big holding tank and plenty of time, your treatment costs would be relatively cheap. The passage of time allows for sediment to fall out of suspension and water to react with the air and return to a more neutral pH. Money will allow the treatment time and holding space to drop. The process of water treatment is constrained by physics in that there is a point when no amount of money will make a process faster.

With this in mind Rampart has a few approaches to the recycling hydrodemolition wastewater dilemma. The newest being the Alar vacuum drum filter which strikes a good balance between the three variables. The Alar requires less space than an elaborate settling tank, sand filter, and pH treatment/storage tank option and it can also achieve the same results in less time.

Alar Unit

While the process to clean up the water to a level where it can be reused in the high-pressure pumps is more expensive than methods that do not involve reuse it may be still economical via viable in situations where:

• Water is scarce and therefore expensive. This can happen on remote jobsites where the tapping of lakes and streams is prohibited or requires excessive treatment to use.
• Water is not available because of a drought emergency. Water restrictions can eliminate all non-crucial uses of municipal, well, or other potable water sources.
• It may be required by the EPA due to discharge requirements.
• Wastewater treatment plants will not accept any new discharges. Sometimes new discharges are not acceptedIn small municipalities or water treatment authorities or the permitting is difficult to obtain in timely manner.

How It Works

The Alar unit uses a continuously renewing filter of diatomaceous earth (DE) which can filter down to half a micron. A filter fabric drum is "loaded" with the DE cake and then fed wastewater at a rate determined by the quality of the wastewater. The drum sits partially submerged in a pan of wastewater which is pulled up onto the drum by the force of the vacuum being applied to the drum. As the DE cake is loaded with concrete fines a blade cuts off the filter media thus renewing the filter. The unit runs until all the water is treated or the cake runs out and needs to be reloaded.

The vacuum actuated blade cuts off the filter media and dried concrete.	The dried concrete waste can be disposed of with regular construction debris.	The recycling unit requires a surge tank to store wastewater during peak discharge while the treatment process is underway.

Large Scale Water Recycling

Depending on the scale of the project and desired production rates, recycling systems can be large or small. The filters, settling tanks, and flocculation tanks have preset residence times that determine how much water can be put through them. A job that requires the usage of three triple trailers, each producing as much as 48 gallons per minute (potentially 140 gpm), may require the usage of a large treatment or surge tank much like the one pictured below. The Alar may still be required to polish the water before is reused, removing as much of the suspended solids as possible.

Traditional water treatment may be required before any final polishing of water for re-use.	Recycling systems can be large or small depending on number of hydrodemolition units running.	17,000 gallon dewatering tank for separating solids from liquids.

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